Comparison Between Gamma-ray and HXR Observations

(Morimoto, Ph.D. thesis, Rikkyo Univ., 1996.)

The 27-October-1991 flare is the most energetic flare observed by Yohkoh
during the last solar cycle.
The left panel shows the intensity of hard X-ray sources
in the impulsive phase, and right, soft X-ray image with hard X-ray source
(contours) superposed.

(Morimoto, Ph.D. thesis, Rikkyo Univ., 1996.)

This panel shows independent hard
X-ray light curves from sources A and B, identified in the images as
the extreme footpoints of the flaring loops. Contrary to typical
behavior in compact loop flares, the footpoints A and B have
independent and only partially correlated variability. The lowest
trace shows the total flux in the 4-7 MeV energy band dominated by
inelastic-scattering gamma-ray lines such as C_12 4.41 MeV. This
emission also shows a different time profile but appears to match -
with a time lag - the correlated component of the A, B emission after
the gamma-ray onset. This evidence suggests strongly that the
main particle acceleration both ions and electrons, took place on
closed magnetic loops spanning the entire flare region.